1. Field of Invention
The present invention relates to an air-cooled oxygen-gas burner for use with a direct fired furnace, and wherein the injection nozzle assembly of the burner has concentric openings which are adjustable to vary the velocity of the gas, oxygen and air injected within the furnace to vary the shape of a flame, and further, wherein the pressure of the gas, oxygen and air is variable to modify the temperature, radiation/convection of the flame.
In particular, the oxygen-gas burner of the present invention was conceived for use in aluminum melting direct fired furnaces, which requires a flame of very high temperature to cause the aluminum to melt quickly so as to reduce the oxidation time in the furnace. As is also known in the art, the flame must also be controllable to produce a high velocity turbulent flame in the initial combustion cycle when the furnace environment and the scrap metal are cold, and to vary the flame characteristic at appropriate times during the melting cycle. For this purpose, variable gas/oxygen/air combustion systems have been developed, and one such system presently used is identified as the "PYRETRON" system (Registered Trademark of American Combustion Inc.) The oxygen is used in the mixture in order to accelerate the oxidation of the fuel inside the hot flame core. The adjustability of the oxygen/air mixture can provide a reduction of the inert nitrogen contained in the air required for complete combustion and the ability to increase the ratio of radiative to convective heat transfer by providing higher flame temperature and lower turbulence due to the reduced overall mass flow. Thus, the flame can be controlled to modify its radiative and convective heat transfer. In the Pyretron system the combustion parameters are controlled in response to changes in the kinetics of the combustion process by controlling the introduction of two distinct oxidizers having different oxygen content, and this can be controlled by programmable logic controllers which monitor the combustion process. This technology is perhaps the most recent development in the art, although other oxygen-gas burners have been developed to achieve the results of reduced energy consumption by 20% in kWh/ton, minimized oxydation and increased production by the shortened melting time of about 40% and of the scrap metal resulting in a production increase of about 20%.
2. Description of the Prior Art
There are, however, some disadvantages of these burner systems, and these can be summarized briefly as follows. One major disadvantage is that, because of the high temperature flame produced by the burner assembly, it is necessary to cool the burner body, and this is achieved by circulating water in a closed system about the body. Great care is therefore required to assure that the risk of water leakage is minimized as, if there were to be leakage of water into the furnace, the contact of water with molten aluminum could cause an explosion. Accordingly, this poses great danger. A still further disadvantage is that the high flame temperature causes rapid degradation of the refractory wall of the furnace, particularly in the environment of the burner nozzle, and accordingly the furnace requires more frequent repair which means that the productivity is affected due to the shut-down time of the furnace required to effect such repair. A still further disadvantage is that the burner nozzle has a very short life as it also deteriorates under the influence of the high temperature flame and the burner must be changed more frequently, thus adding to the cost of the operation.